<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <style>
        .box {
            width: 400px;
            height: 400px;
            /* 线性渐变 */
            /* background-image: linear-gradient(to bottom, red, red, blue); */
            /* 方向: */
            /* to right */
            /* to bottom right */
            /* 30deg */
            /* 径向渐变 */
            background-image: radial-gradient(black, white, black, white, black, white, black);
            border-radius: 200px;
        }
    </style>
</head>
<body>
    <div class="box"></div>
</body>
</html>